/Engine/Plugins/Experimental/Mutable/Source/MutableTools/Public/MuT/NodeMeshClipMorphPlane.h
Define an axis-aligned box that will select the vertices to be morphed. If this is not set, or the size of the box is 0, all vertices will be affected. Only one of Box or Bone Hierarchy can be used (the last one set)
void SetVertexSelectionBox ( float centerX, float centerY, float centerZ, float radiusX, float radiusY, float radiusZ )